Movies like The Kid Who Would Be King

If you want that specific blend of Arthurian mythology, coming-of-age heart, and humor-laced action with a scrappy band of misfits, Willow and Dragonslayer probably scratch the itch most reliably—both center reluctant young heroes assembling unlikely companions against dark magic with mentor figures guiding them toward improbable victories. The Sorcerer's Apprentice might also hit if you're after that modern-world-meets-ancient-magic tone with a wise mentor and supernatural combat, though it skews slightly more action-heavy and less ensemble-focused than the film you're referencing. The rest of these share either the mentor-apprentice dynamic, the Arthurian framework, or the found-family-forged-in-adversity theme, but none quite nail all three elements the way those first two do.